NOISE HAZARD, WORKPLACE NOISE, DBA, HEARING LOSS, SOUNDPROOFING
Soundproofing
NOISE HAZARD,
WORKPLACE NOISE, DBA, HEARING LOSS, SOUNDPROOFING
Non-Industrial Noise
Sound is a natural phenomenon that reflects the movement or
pressure changes that occur in the surrounding environment. Humans experience
man-made sounds that are produced by traffic e.g. that emitted by air, sea, and
road transportation]; construction activities; machinery air conditioning
plants, fans, or leisure activities [e.g. music, radio, TV, or public address
systems.
However, the sound that is universally experienced by
everyone from an early age is speech, which is used for daily communication. A
healthy human ear can distinguish sounds in the frequency bandwidth of 20 Hz–20
kHz.
Noise, on the other hand, is the combination of unwanted,
interfering, and often irritating sounds, regardless of their source.
Workplace Noise
Employees’ exposure to excessive noise is a recognized potential
health hazard. Such exposure may occur during outdoor activities such as
working with air compressors, pumps, turbines, boilers, diesel/petrol engines,
diesel generators, air coolers, fin fan coolers, heat exchangers, vents, and
flares, or from indoor activities such as grit sandblasting or maintenance
workshops.
The sound levels in the
workplace the following shall be considered:
·
Observation of specific working practices e.g.
Workers not wearing assigned HPE
·
Relevant information about equipment noise as
per manufacturers’ specifications
·
Workers exposed to ototoxic substances or
vibration
·
Identification of high-risk SEGs prone to
excessive noise
·
The noise risk assessment shall consider the
following factors
·
Frequency and duration of exposure including any
exposure to peak sound level
·
Availability of alternative equipment designed to
reduce the emission of noise e.g. mufflers, acoustic barriers, dampers, etc.
·
Appropriate information obtained from health
surveillance i.e. audiograms
·
Availability of personal hearing protectors with
adequate attenuation characteristics
HUMAN EAR &
HEALTH EFFECTS OF NOISE
The ear is a complex organ that is sensitive to very soft
sounds e.g. whispers but can also receive loud sounds e.g. bangs, cracks, and
shouting. However, as the sound pressure becomes louder, the ear experiences
pain, and in high medium cases the eardrum may burst.
Prolonged exposure to loud noise, whether it happens
socially or through work-related i.e. occupational activities can lead to
Noise-Induced Hearing Loss (NIHL). This condition is the result of sound
pressure impacting the microscopic hair cells known as Cilia (receptor) located
in the middle and inner regions of the ear, causing permanent damage and death
to these cells leading to the disability to transmit a sound signal to the
brain.
NIHL starts with loss of hearing at 4000 Hz (audiometric
notch) and then spreads across the different frequency bandwidths. The loss is
manifested by the person not understanding certain letters during speech or
listening to TV, radio, or other forms of communication. For long-term
exposures to high levels of Noise, the full range of audible frequencies is
lost, thus leading to total deafness. The exposed person may also develop
tinnitus (i.e. ringing, whistling, buzzing, or humming in the ear) leading to
disturbed sleep and general social life.
THE NOISE SOUND SCALE
Sound is generated from a broad spectrum of pressure changes
that happen near and at the ear. As a result, sound pressure has to be measured
on a base 10 logarithmic scale, which is known as the Decibel (dB). The
pressure measurement is also suffixed by one of the letters A or C (e.g. dBA or
dBC) to indicate that an electronic frequency filter [i.e. an electronic
weighting] has been used during the measurement.
The weightings, enable the Sound Level Meter (SLM) to
respond to the same frequencies as those recognized by the human ear. The three
weightings correspond to the following settings:
·
Weighting is the noise that the human ear can recognize.
·
Weighting is impacted.
·
Weighting is the flat frequency response of 8Hz
to 20 kHz (± 1.5dB). It is the actual noise that is made with no weighting at
all for the human ear (Z for zero). Often used in octave band analysis and for
determining environmental noise such as peak level in mining and blasting due
to extremely low frequency of the shock wave.
CHARACTERISTICS OF SOUND
The main features of sound are outlined below:
Intensity
Sound intensity is defined as the sound power per unit area.
The usual context is the measurement of sound intensity in the air at a
listener’s location.
Frequency
Human hearing is sensitive to sound that occurs in the
frequency band of 20 Hz to 20 kHz, but workplace sounds are composed of a broad
spectrum of frequencies, some of which occur in the hearing range, while others
do not [e.g. ultrasound or very low-frequency sound]. For that reason, when
conducting risk assessments of noise at work, the audible frequency range is
sometimes divided into smaller bandwidths for the measurements to be used for
profiling noise especially from plants and machinery, or for evaluating noise
control and the efficacy of hearing protection equipment. The most common
bandwidths are the Octave [1/1] and Third [⅓] Octave.
The frequencies usually included in the Octave are 63, 125,
250, 500, 1000, 2000, 4000 & 8000
Hz. On the other hand, the ⅓ Octave is divided into 36
frequencies between 6.3 Hz and 20 kHz.
Time
There are three time-related noise sources commonly
encountered in the workplace. These are described below.
·
Sources with noise levels that fluctuate by more
than ±3 dB are generally defined as variable or intermittent. These sources are
characterized by long periods of silence which are followed by a loud noise. A
typical example is the intermittent use of angle grinders or metal saws in
welding and fabrication shops or the use of road and stone breakers during
civil works.
·
Continuous or steady-state sources produce
uninterrupted sound, varying by less than ± 3 dB. Typical examples are
compressors, fans, motors, boilers, generators, and reverse osmosis plants.
·
Impulse or impact is characterized by a sharp
rise and rapid decay in sound levels and is less than 1 second in duration.
These are generated when a collision occurs between two solid objects or by a
rapid pressure release. Typical examples are hammering on metal surfaces, dropping
heavy objects, doors slamming shut, opening pressure release valves, etc.
WORKPLACE NOISE CONTROL REQUIREMENTS
Evaluation and control of workplace noise hazards shall
observe the requirements provided in this standard. The following requirements
shall be adopted for employee hearing protection:
·
All areas with continuous noise levels exceeding
85 dBA shall be considered high noise areas.
·
During presence in an area or around equipment
where noise levels are 85 dBA or higher, ear protection shall be required at
all times.
·
All new projects shall be engineered, where
reasonably practical, to meet the 85 dBA noise level limit.
·
Permanent high noise areas shall be identified
with warning signage at normal points of entry.
CONTROL OF NOISE AT WORK
International best practice such as the UK HSE Noise
Regulations 2005 requires organizations to prevent or reduce risks to the health
of their employees from exposure to noise at work. In this regard:
·
Assess the risks to employees from noise at work
·
Take actions to reduce the noise exposure that
produces those risks
·
Provide employees with hearing protection, if
the noise exposure cannot be sufficiently reduced by using other methods
·
Ensure the established limits on noise exposure
are not exceeded
·
Provide employees with information, instruction,
and training on noise limits and relevant controls
HEARING CONSERVATION
PROGRAM (HCP)
Exposure Monitoring
·
The Company competent person to develop and implement
a monitoring program and sampling strategy to assess employee’s exposure to
noise
·
The sampling strategy shall be designed to
identify employees for inclusion in the hearing conservation program and to
enable the appropriate selection of hearing protection;
·
All continuous, intermittent, and impulse sound
levels from 85 dB(A) and above shall be integrated into the noise measurements.
·
Instruments used to measure employee noise
exposure shall be calibrated as per the manufacturer’s recommendations to
ensure measurement accuracy.
· Monitoring shall be repeated whenever a change in production, process, and equipment or control measures increases noise exposures.
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